HeliumIt is the lighter-than-air gas that makes a party balloon float ﻿up to the ceiling, but a shortage of the element is threatening to disrupt critical research projects.In 1996 the US government decided to start selling off its national helium reserve at rock-bottom prices, leading to a glut of cheap helium on the world market. Scientists believe this explains why oil companies have not bothered to collect much of the helium released to the air during the mining of natural gas. With the entire US strategic reserve expected to be sold off by 2015, irrespective of the market price, several multimillion-pound projects in the UK have had to be put on hold.The supply of helium, an inert element with the lowest boiling point of any known substance, has now become so erratic that scientists are calling for a ban on all but the most essential uses – which could mean no more helium-filled party balloons. “The scarcity of helium is a really serious issue. I can imagine that in 50 years’ time our children will be saying ‘I can’t believe they used such a precious material to fill balloons,’” said Peter Wothers of Cambridge University, who gave the 2012 Royal Institution Christmas lectures.“There is a finite supply of this lighter-than-air gas on Earth so if we keep using it for non-essential things like party balloons, where we’re just letting it float off into space, we could be in for some serious problems in around 30 to 50 years’ time,” Dr Wothers said.The shortage has mainly affected research centres studying the brain using magnetoencephalography (MEG) scanners, which are similar to the MRI machines used in hospitals but need to be topped up regularly with liquid helium (helium super-cooled to minus 269C, just four degrees above the lowest possible temperature, absolute zero).Last year, MEG scanners at the universities of Glasgow, London, Oxford and Cambridge were all affected by shortages of helium. “We increasingly face regular periods of forced shut-down of our multimillion-pound facility because of these difficulties, and we are told the problem will only get worse,” said Mark Stokes, a cognitive neuroscientist at Oxford’s Centre for Human Brain Activity.“It is difficult to imagine an adequate market incentive to collect helium during natural gas extraction while the US government is selling off its entire stockpile at bargain prices,” Dr Stokes said.“Cheap helium also drives misuse. A staggering 8 per cent of the world’s helium supply is currently used for filling party balloons,” he said.Even though helium is the second most common element on Earth, only a finite amount is available for use and this store is non-renewable. Some experts suggest supplies could be depleted by the middle of the century.Liquid helium is critical for the cooling of infrared detectors, nuclear reactors and the machinery of wind tunnels. It is also a vital ingredient of the space industry: Nasa uses the inert gas to purge potentially explosive fuel from its rockets.Professor Ray Dolan of University College London leads the Wellcome Trust Centre for Neuroimaging, which had stop taking bookings for its scanner in 2012 because of helium shortages. “We have now had to invest in expensive helium-capture technology to recover some of what is burnt off,” he said, “and this decision was driven by a need to insulate ourselves against uncertainty over supply and cost.”Helium is also critical for the massive magnets used by the Large Hadron Collider at the European Organisation for Nuclear Research (Cern) in Geneva. Serge Claudet, who leads the LHC’s work on cryogenics (the branch of physics dealing with the production and effects of very low temperatures), said Cern’s vast size has helped to insulate it against the recent vagaries of the helium market. Unlike most smaller scientific centres Cern can afford to use two or three helium suppliers, helping to keep its costs down.“It’s like any industry: you have to be protected against fluctuations in the cost of a raw material, and for us helium is a strategically important raw material because without it we would not be able to function,” Dr Claudet said.